A pump utilized in a downhole tool may be driven by an electrical motor that is either (1) directly coupled to a piston via a linear transmission system such that rotation results in linear motion, or (2) coupled to a hydraulic pump, thus creating a high pressure line, such that routing the high pressure line and the hydraulic reservoir line in the proper chambers of a secondary piston system results in the linear motion. The result is either a pump mechanism or, more generally, a mechanical stroking device. However, such systems may be limited with regard to electrical power supply and/or other factors, some of which may be related to their implementation in small diameter tools and their operation at high temperature. There are also hydrostatic powered mechanisms, but they are generally designed for a single actuation. As a result, such as in water or air cushion sampling, an air chamber is utilized instead of the formation pressure to activate a piston and withdraw fluid from the formation. Once the sample chamber is full, however, further movement of the piston may be limited, if not impossible.